I miss the correct long version "Do que é que eles são feitos?" But I am not expecting anyone to say this anymore
You could understand it in English as something like: "what is it that they are made of?"
More correctly, the translation might be 'of what is it that they are made?' However, I agree that this would rarely be used these days, especially when spoken rather than written. Interesting, though, that the original portuguese sentence retains this structure.
In written English, the highly formal version would be "Of what are they made?"
The hints say that "feitos" means "deeds", "feats" and "likes". So this sentence must have some kind of expression. What is it?
Yes, I realized that after posting my question. Those hints can be very confusing. I had learned yesterday that past participles can be pluralized. This sentence's structure is preposition - question word - plural pronoun - auxiliary verb - plural past participle.
If you look closely, "deeds" are the actions made by a great man. Did you notice the "made"?
That's a form of sentence in which we transform the adjective into a noun: "Seus feitos são grandes" = "His deeds are great"
Does this sentence refer to people in a metaphorical sense, as well as objects in a physical sense? In English, we say what someone is made of as a way to express their character. With regard to objects, it would simply be their physical composition.
Yes, a participle used with the verbs "ser", "estar" and other linking verbs will change according to the noun it refers to: "a palavra foi dita" (the word was said). But with the verb "ter", the participle is invariable: "ela tinha dito" (she had said).
Yes, these participles are very similar to adjectives. Makes also semantic sense, they describe properties more than actions/activities, so it also makes sense to apply the same rules for them (inflection).